Two of the most popular back-end data stores Web developers work with today are MySQL and SQL Server. They are fundamentally similar in that both are data storage and retrieval systems. You can use SQL to retrieve data with either because both claim support for ANSI-SQL. Both database systems support primary keys and key indices, so you can also create indices used simply to speed up queries and for constraining input. Further, both provide some form of XML support.

Aside from the obvious difference of price, what distinguishes these two products from each other, and how do you choose between them? Let's take a look at the core differences between these two products, including licensing costs, performance, and security.